For a few years and in the interest of the ecology, low sulfur fossil fuels were used in the generation of energy by the combustion of low sulfur coal and similar low sulfur carbonaceous materials.
Depleting fuel reserves, however, have dictated the necessity of combusting fossil fuels of high sulfur content.
With this, considerable interest has developed in the ability to combust high sulfur fuels and still emit a flue gas to the atmosphere which is sufficiently low in the oxides of sulfur that a problem will not be presented from an ecology standpoint.
Many processes have been proposed for the removal of the oxides of sulfur from the stack gases emitting from the boiler sections of power generation systems.
Most are complicated and involve additional operating and maintenance expense in addition to high initial capital cost for new installations. They are also cumbersome and costly to adapt to existing installations.
Some involve rejection scrubbing operations, which entail additional raw materials and material handling cost, add nothing to fuel efficiency, rather decrease it, and result in slurry disposal problem.
In another process, sulfur dioxide is scrubbed from the gas and regenerated as sulfur dioxide. Operating costs are high and the oxides of nitrogen introduce complications to sulfur dioxide removal. Further, sulfur dioxide is not a desirable by-product and must be converted to sulfuric acid or to sulfur at a considerable additional expense.